Method for storing hydrosols in a dry reusable state



Unite States Patent METHOD FOR STORING HYDROSOLS IN A DRY REUSABLE STATE1 ingsworth, Rochester, N. Y., assignors to Eastman Kodak Company,Rochester, N. Y., a corporation of New Jersey No Drawing. ApplicationDecember 14, 1953 Serial No. 398,235

5 Claims. (11. 260-8) This invention relates to a method for the drystorage of polymeric hydrosols by which those dry materials may bereadily redispersed in aqueous liquids.

There are many polymeric hydrosols which are of value in compositionssuch as coating compositions and the like. However, it has been acharacteristic of those hydrosols heretofore that when the liquidcontent thereof is removed the resulting solid material has not beencapable of redispersion. Consequently, when shipping or storage of thosematerials is indicated the bulkiness of the hydrosols creates a problemwhich would be avoided if only the solid portion of those hydrosolscould be handled.

One object of our invention is to provide a method for convertingpolymeric hydrosols to a dry form in a state in which redispersion maybe readily accomplished.

Other objects of our invention will appear herein.

2,856,371 Patented Oct. 14, 1958 ice cedure are of high quality. Also wehave found that the photographic quality of the hydrosols is notadversely affected by preparing in dry form in accordance with our Wehave found that polymeric hydrosols may be safely dried down to a formwhich admits of redispersion if there is added to the hydrosol an amountof gelatin at least equal to the amount of the hydrosols, based on thedry weight of each, prior to the drying operation. The product soobtained can be stored for long periods of time and when the material isdesiredin dispersed form the dried materials will readily admit ofdispersion in water or some other liquid in which water predominates.

The method of carrying out our process involves the dispersing of thepolymeric hydrosols made up of discrete dispersed particles in a gelatinsolution in a proportion that the gelatin constitutes at least equalparts to the hydrosol figured in terms of dry weight. The compositionthus prepared may be set by chilling and the drying may then beaccomplished in any manner conventional to the drying of gelatin. Theproportion of gelatin to hydrosol, dry weight, should be within therange of 9:1 to 1:1. If an amount of gelatin much below this range isemployed the hydrosol is denatured by drying, that is, redispersion willnot take place. Itseems as if the gelatin forms a protective coating forthe particles of the hydrosol and preserves that dry material in such aform that the water readily disperses those particles.

In the carrying out of our invention there is no need to make anyradical adjustment in the condition of the gelatin as the preparation ofthese dispersions at a pH of 6, which is the pH at which gelatindispersions are generally obtained, is suitable. We have also found thatthe preparation of the dispersions at 10% gelatin concentration workssatisfactorily in the carrying out of our invention although, of course,other concentrations can be employed and the desired effect will beobtained. After the composition of gelatin and the polymeric hydrosolhas been prepared, the mixture of gelatin and hydrosol can beconveniently converted to the form of noodles or slices such as bychilling which sets the gelatin. These particles may be washed with coldwater pripr to drying and also any water soluble impurities whichmigMtbe present may be removed by such a washtures were found to readilyredisperse.

.. 5 John w. Gates, Jr., John R. Dann, and Bernard 1). Ill- "invention.The dry compositions thus obtained may be stored for long periods or maybe redispersed after holding for any convenient time such as Whereshipping of the hydrosol material is desired. The polymeric hydrosolswhich may be handled or stored in accordance with our invention may beany of the latices which are well known as useful for coatingoperations, may be a polymeric hydrosol such as the type described andclaimed in U. S. applications Serial Nos. 398,234 and 398,236 of Gatesand Fowler and Gates, Dann, and Illingsworth, respectively, whichapplications are being filed of even date, or the polymer may be apolymeric hydrosol of the type described and claimed in U. S.applications Serial Nos. 272,709 and 336,431 of Fowler, filed February20, 1952, and Febuary 11, 1953, respectively. Any other polymerichydrosols of a similar nature may be handled and stored as desired inaccordance with our invention. The following examples illustrate ourinvention:

Example 1 A hydrosol was prepared having a 20% solid content in thepreparation of which sodium lauryl sulfate and a mixture of 59 parts ofn-butylacrylate, 25 parts of 'acrylonitrile and 16 parts of 5% maleatedglue was emsliced, washed, when necessary, and dried in the con:

ventional manner. The resulting material was obtained in the form offlakes. To redisperse the dry flakes they were soaked in water at 25 C.for /2 hour and then warming to 50 C. accompanied by stirring. The mix-The hydrosol was prepared. in accordance with the procedure described inthe Gates and Fowler application filed of even date herewith.

Example 2 A hydrosol was prepared by an emulsion polymerization asdescribed in our application filed of even date using sodium laurylsulfate as the micell-formi'ng surface active agent. The reaction masswas composed, of 49 parts of nbutylacrylate, 21 parts of acrylonitrileand 30 parts of glue, these materialsbeing present in a proportion of20% of the mass. The hydrosol thus prepared was mixed with gelatin inratios of 9:1, 7:3 and 1:1, dry weight, gelatin to hydrosol. It was,found that these mixures after drying are susceptible to redispersion inwater.

Example 3 A hydrosol having a 20% solids content was prepared of amixture of 49 parts of n-butylacrylate, 21 parts of styrene, and 30parts of glue by an emulsion polymerization as described in ourapplication filed of even date with sodium lauryl sulfate employed asthe micell-forming surface active agent. This preparation follows theteachings of the Gates and Fowler application referred to above. Thehydrosol was mixed with gelatin in the ratios of 1:9, 3:7 and 1:1, dryweight, and the mixtures were dried. It was found that these drycompositions can be readily redispersed in water whenever desired.

Example 4 A hydrosol Was prepared by the emulsion polymerization of amixture of 84 parts of n-butylacryllate and 16 parts of 5% maleated glueso as to form a hydrosol hay ing a 20% solids content. The hydrosol thusprepared was mixed with gelatin in ratios of 9:1, 7:3, 1:1, the ratiosin every case being by dry weight. The compositions thus obtained weredried and were found to be readily .susceptible to redispersion in waterwhen such a dispersion is desired.

Example 5 A hydrosol was prepared by the emulsion polymerization of amixture of -49 parts of n-butylacrylate, 21 parts of styrene and 30parts of 5% maleated glue at a solids content with sodium laurylsulfate. The hydrosol thus prepared was mixed with gelatin in the ratiosof gelatin to hydrosol, dry weight, of 4:1, 7:3, 3:.2.,and 1:1 in thesame manneras described in Example 1. It was found that the driedmaterials would redisperse in water when the preparation of a dispersionwas desired.

Example 6 .A polymeric hydrosol was prepared of a mixture consisting of49 parts of n-butylacrylate, 21 parts of .styrene, and parts of 5%maleated glue using a 10% solids concentration. The hydrosol thusprepared was mixed with gelatin and treated as described in Example 1,the ratios of gelatin to hydrosol by dry weight being as follows: 4: 1,7:3, 3:2, 1:1. The dried material was susceptible to redispersion inwater when the preparation of a dispersion thereof was desired.

Example 7 A hydrosol was prepared by the emulsion polymerization of amixture of 20% solids content of 42 parts of nbutylacrylate, 42 parts ofstyrene, and 16 parts of methacrylamide in the presence of a surfaceactive agent, this emulsion polymerization having been carried out astaught in U. S. application Ser. No. 272,709 of William F. Fowler, I r.The hydrosol thus prepared was mixed with gelatin in ratios of gelatinto hydrosol, by dry weight, of 9:1, 7:3 and 1:1 and the mixtures thusobtained were dried in the manner taught in Example 1. The driedmaterials were found to be readily susceptible to redispersion in water.

Example 8 A styrene-butadiene latex of 20% solids content was mixed withgelatin in the ratios of 9:1, 7:3, and 1:1 gelatin to latex by dryweight. These mixtures were dried in the manner taught in Example 1. Thedried materials were found to be readily susceptible to redispersion inwater.

We claim:

1. A method of handling polymeric hydrosols which comprises mixing 1part of a polymeric hydrosol resulting from an emulsion copolymerizationin which one ofthe monomers employed therein was selected from the groupconstisting of the alkyl acrylates, the alkyl methacrylates, butadiene,isoprene and chloroprene, and in which the other monomer is at least oneof the group consisting of 4 styrene, acrylonitrile and methacrylamide,with 1-9 parts of an aqueous solution of only gelatin, all by dryweight, converting the mass to solid form by chilling, dividing the massinto small independent units and substantially completely drying thoseunits and later redispersing the units in water.

2. A method of handling polymeric hydrosols which comprises mixing 1part of a polymeric hydrosol resulting from the emulsioncopolymerization of a mixture of an alkyl acrylate, acrylonitrile, and agelatin compound selected from the group consisting of gelatin and theunsaturated acid derivatives of gelatin with 1-9 parts of an aqueoussolution of only gelatin, all by dry weight, converting the mass tosolid form by chilling, dividing the mass into small independent unitsand substantially completely drying those units and later redispersingthe units in water.

3. A method of handling polymeric hydrosols which comprises mixing 1part-of a polymeric hydrosol resulting from the emulsioncopolymerization of a mixture of an alkyl acrylate, styrene, and agelatin compound selected from the group consisting of gelatin and theunsaturated acid derivatives of gelatin with l-9 parts of an aqueoussolution of only gelatin, all by dry weight, converting the mass tosolid form by chilling, dividing the mass into small independent unitsand substantially drying those units and later redispersing the units inwater.

4. A method of handling polymeric hydrosols which comprises mixing 1part of a polymeric hydrosol resulting from the emulsioncopolymerization of an alkyl acrylate, styrene, and methacrylamide with1-9 parts of an aqueous solution of only gelatin, all by dry Weight,converting the mass to solid form by chilling, dividing the mass intosmall independent units and substantially completely drying those unitsand later redispersing the units in water.

5. A method of handling polymeric hydrosols which comprises mixing 1part of styrene butadiene copolymer latex compatible with gelatin with19 parts of an aqueous solution of only gelatin, all by dry weight,converting the mass to solid form by chilling, dividing the mass intosmall independent units and substantially completely drying those unitsand later redispersing the units in water.

References Cited in the file of this patent UNITEDSTATES PATENTS1,762,494 Wescott June 10, 1930 2,019,055 Noble Oct. 29, 1935 2,500,028Griggs et al. Mar. 7, 1950 2,548,520 Damschroder et al Apr. 10, 19512,739,137 Fowler Mar. 20, 1956 FOREIGN PATENTS 213,886 Great BritainJune 19, 1924 OTHER REFERENCES Noble: Latex in Industry, published byPolmerton Publishing Co.,'September 1953, 2nd edition, page 148.

1. A METHOD OF HANDLING POLYMERIC HYDROSOLS WHICH COMPRISES MIXING 1PART OF A POLYMERIC HYDROSOL RESULTING FROM AN EMULSION COPOLYMERIZATIONIN WHICH ONE OF THE MONOMERS EMPLOYED THEREIN WAS SELECTED FROM THEGROUP CONSISTING OF THE ALKYL ACRYLATES, THE ALKYL METHACRYLATES,BUTANDIENE, ISOPRENE AND CHLOROPRENE, AND IN WHICH THE OTHER MONOMER ISAT LEAST ONE OF GROUP CONSISTING OF STYRENE, ACRYLONITRILE ANDMETHACRYLAMIDE, WITH 1-9 PARTS OF AN AQUEOUS SOLUTION OF ONLY GELATIN,ALL BY DRY WEIGHT, CONVERTING THE MASS TO SOLID FORM BY CHILLING,DIVIDING THE MASS INTO SMALL INDEPENDENT UNITS AND SUBSTANTIALLYCOMPLETELY DRYING THOSE UNITS AND LATER REDISPERSING THE UNITS IN WATER.